A radar sensor with an antenna using a signal of a millimeter or submillimeter wave of 20 GHz or more is known. Radar sensors appropriate for miniaturization or lower costs have been proposed. In such a radar sensor, active circuits such as an oscillator and mixer and an antenna constituting the radar sensor are formed on the same semiconductor substrate and configured as one-chip MMIC (Monolithic Microwave Integrated Circuit). Further, the MMIC is sealed in a resin package. In this radar sensor, an electromagnetic wave is radiated in a desired direction by a dielectric lens mounted on an upper portion of the antenna.
It is necessary to form a dielectric lens on the resin package to radiate an electromagnetic wave in a desired direction and thus, the package has a protruding structure, leading to a thicker package as a whole. It is also necessary to optimize the position and/or shape of the lens in accordance with the position and/or shape of the antenna, creating a problem of low versatility of the package.